Bobbing machine



W. S. PRAEG HOBBING MACHINE Dec. 15, 1953 3 Sheets-Sheet 1 Original Filed June 7, 1948 INVENToR. WALTER SPRAEG ATTO R N YS W. S. PRAEG HOBBING MACHINE Dec. 15, 1953 3 Sheets-Sheet 2 Original Filed June 7. 1948 f ///////////Vv INVENTOR.

WALTER $.PRAEG BY www ATTORN YS W. S. PRAEG HOBBING MACHINE Dec. 15, 1953 5 Sheets-Sheet 5 Original Filed June '7, 1948 FIC-3.6.

K INVENTOR. WALTER s PRAEG BY www) ATTORNEYS Reissued Dec. 15, 1953 HOBBING MACHINE Walter S. Praeg, Detroit, Mich., assignor to National Broach & Machine Company, Detroit, Mich., a corporation'of Michigan Original No. 2,528,242, dated October 31, 1950, Se-

rial No. 31,421, June 7, 1948.

Application for reissue October 15, 1951, Serial No. 251,264

Matter enclosed in heavy brackets appears in the original patent but forms no part of this reissue specification; matter printed in italics indicates the additions made by reissue.

9 Claims.

The present invention relates to a hobbing machine.

It is an object of the present invention to provide a hobbing machine characterized by sturdy construction, the economy with which it may be built, and the accuracy and ease of setup change for hobbing helical gears and spur gears.

It is a further object of the present invention to provide a hobbing machine including means responsive to relative traverse between the gear and hob for imparting a compensating relative rotation thereto.

It is a further object of the present invention to provide a hobbing machine in which angular adjustments may be made between the direction of the axes of the gear and hob and the direction of relative traverse between the gear and hob.

It is a feature of the present invention to provide a hobbing machine including interconnected drive means for rotating the hob and a Work gear, independent means for eifecting relae tive traverse between the hob and Work gear, and compensating means automatically operable in response to relative traverse between the hob and Work gear for compensating for such relative traverse.

Other objects and features of the invention will become apparent as the description proceeds, especially when taken in conjunction with the accompanying drawings, wherein:

Figure 1 is a iront elevation of a hobbing machine constructed in accordance with the present invention.

. Figure 2 is an enlarged fragmentary section on the line 2-2 of Figure l.

Figure 3 is a section on the line 3--3 of Figure 2.

Figure 4. is a fragmentary plan view.

Figure 5 is a sectional View through the work spindle transmission of a simplified form of the machine, and

Figure 6 is a fragmentary section on the line E-E of Figure 2.

Hobbing machinesgenerally are provided with means for driving the hob and the work gear and for effecting relative traverse between the .hob and Work gear all in denitely timed rela- '.tion. Accordingly, it has been impossible to eiect rapid return traverse after the hobbing cut has which include a diiferential in the train of gears driving the work gear, this differential including a gear driven in accordance with the rate of hrelative traverse between the gear and hob, Such diiferential hobs, however, are unduly complicated and expensive to manufacture, require involved computations when seeking changes in setup, and necessarily introduce inaccuracies in the iinished gear as a result of a long train of driving gears which serve to introduce backlash.

In accordance with the present invention rotary drive to either the hob or the gear includes a rotating drive element having helical surfaces thereon and adapted to slide axially along a correspondingly formed element in accordance with relative traverse between the gear and hob. As the helical surfaces referred to may be of the same effective lead as the gear being hobbed, it will be apparent that relative traverse between the gear and hob may be at any rate desired and that completion of a rough hobbing stroke may be followed by rapid traverse to starting posi tion followed by a relatively rapid finishing hobbing operation. The machine is designed to fae cilitate change-over by substitution of the parts providing the mating helical surfaces, and it is also contemplated that the parts having the mating helical surfaces need not be changed but that change gears may be introduced into the train so as to compensate for gears of different helix angles.

Referring now to the drawings the hobbing machine is illustrated as a horizontal spindle machine in which relative traverse between the hob spindle and the Work spindle takes place in a horizontal plane. It will be appreciated, however, that the only important consideration is to maintain relative motions between the hob spindle and the gear spindle constant.

As best seen in Figures 1 4, the hobbing machine comprises a main frame or casting Il) providing a horizontal bed Il having ways indicated at I2 formed thereon. Overlying the bed I2 is a vertically adjustable hob slide l5 which is mounted in ways indicated at I6 on the frame I0. As best seen in Figure 4 the hob slide l5 is located at a corner of the frame I0 so that access to the space between the hob slide l5 and the bed Il is provided at two adjacent sides of the machine. This construction contributes to the rigidity of the parts and hence to the accuracy of the finished gears. At the same time, it affords convenient access to the manually adjustable parts as will subsequently be described,

Mounted for traverse in the ways l2 is a work carriage 20, upon which a work support 25 is mounted for angular adjustment about a vertical aXis. The work support 25, as best seen ln Figure 2, includes a depending circular porso that the Work support may be locked in' angularly adjusted position with respect to the work carriage .20.

In like manner, a hob support is secured 'to the hob slide I5 in angularly adjustable relation with respect thereto. A circular T slot 3| is 'provided which cooperates with clamping bolts 31 Y so that the hob support 30 may be locked in ang'ularly adjusted position.

The hob slide l5, as previously noted is verf tically adjustable in the V,ways I6 and to eiect this vertical adjustment 'a handwheelv 35 is; provided which drivesa vertical adjusting screw at through bevel gearing indicated generally at 31. The screw 36 is received in a threaded block -38 rigidly secured to the upper portion of the frame l0, so that rotation lof the handwheel effects vertical adjustment of the hob slide I5 as will be readily apparent. In order to permit the vertical 'adj'ustment of the hob to be made Without aiecting the drive gearing for the hob, thisV gearincludes a vertically extended splined'shaft 40 which lis slidable in a splined sleeve 4I mounted in a forwardly extending portion 42 of the frame I0. v

Means are provided for effecting rotation of hob Vand work spindles in timed relation, and in the present machine this mechanism is employed to rotate the hob and Workspindles at the relative rates which would be appropriate for gearing having the same number of teeth as the hob and work gear. In other words, no change in relative speed or rotation of the hob and work spindles is provided for in this driving mechanism to compensate for. relative traverse, this compensation being introduced by independent mechanism as will subsequently be described. The drive mechanism comprises a motor 45 carri'ed in the hollow upper portion of the frame |0 which is connected by a suitable coupling 46 to a gear 41. The gear 41 meshes with a gear 4B mounted on a shaft 49 which in turn carries a Worm 50. The Worm 50 meshes with a worm gear 5| which is mounted on a shaft 52. The shaft 52 carries a bevel, gear 53 which eventually transmits rotation to the hob spindle and also carries a Worm gear 54 which eventually transmits rotation to the work spindle. Thus the means for rotating the Work and the hob spindles compri-ses trains of gearing which include a common gear member, this member being the Worm 50. Accordingly, the relative rate of rotation of the. Work spindle and hob spindle is denitely timed and the rate of rotation may be altered by substituting change gearing for the gears 41, 48.

Referring rst to the gear train for rotating the hob spindle the bevel gear 53 .meshes with a bevel gear 50- providedon the sleeve 4|, the bevel gear 60 transmitting rotation to the splined shaft 40` previously referred to. At the lower end of the splined shaft 40 is a bevel gear 6| which is coaxial with the axis of adjustment of the hob support 30. port 30 is provided with a shaft 62 carrying a bevel gear 63 meshing with the bevel gear 6|, so that the meshed relationship of the bevel gears 6|, 63 is maintained during angular adjustment kof the hob support 3s. At the outer end of the shaft 62 is a balance Wheel 64 and intermediate The angularly adjustable hob supeaves 4 of its length the shaft 62 is provided with a gea 65. The hob. spindle is indicated at 61 and is provided with-a gear 68 meshing with the gear 65. Preferably the outer end of the hob spindle 61 is supported as by bearing means indicated at 10 and the spindle supports the hob H.

; The mechanism for rotating the Work spindle includes a worm gear 75 meshing with the Worm 54 and. mounted on a shaft 16 which carries a first change `gear 3.1. A second change gear 18 mounted onv the 'shaft 19 is provided and the shaft 16 carries a driving Worm 80 which drives large worm gear 8|. The worm gear 8| is `mounted in bearings indicated at 82 and has keyed or otherwise secured thereto an internally helically splined sleeve 83v which extends parallel to the Ways l2 provided on the bed The -worke'arrlage 20 .Lisi provided with a shaft 85 mounted in suitable bearings indicated at 86, the shaft having keyed or otherwise secured thereto an externally helically splined member 81 which is slidably received Within the internally helically splined sleeve 83.

At its end the shaft 85 is provided with a bevel gear 00 which meshes with a bevel gear 9| mounted on the Work carriage 26. The bevel gear 9| is disposed with its axis extended vertically and coaxial with the axis of adjustment of tle work support 25. relative to the work carriage 2 The angularly adjustable Work support 25 is provided with a short shaft carrying a first Vbevel gear 06 which meshes with the bevel gear 0I and carrying at its opposite end a second bevel gear 91 meshing with a bevel gear 38 carried by the work spindle |00. The arrangement is such that 'the driving relationship is maintained to the work spindle While the work support 25 isv angularly adjusted about a vertical axis. A tail stock indicated at 10| is provided including a handwh'eel |02 and a center |03 for engaging work supporting means such as the arbor |04 on 'Whichthe Work W is mounted From the mechanism just described, it will be 'apparent that traverse of the work carriage 20 on the bed will superimpose a compensating;Y

rotation upon the rotation of the Work piece W in accordance 'with the lead of the splined members '03, 81.

Means entirely independent from the mechanism for k'rotating the work and hob spindles i's provided for effecting relative traverse of the Work carriage 20. This means comprises a mo- "tor Il 0 carried in the base I0 which drives change Igears and |I2 and hence the shaft |I3. Keyed on the shaft ||3 for axial sliding movement thereon is a speed change gear comprising a `relatively large gear |I4 and a relatively v'small gear |15. Parallel to the shaft I|3 is the traverse shaft ||`6 on which is secured a relatively small gear ||1 and a relatively large gear "|"|0. A 'shifting lever |20 is provided for shifting the gears ||4 and ||5 longitudinally on the shaft |`|3` so that therelatively small gear ||5 may mesh withthe relatively large gear l|8 or Valternatively the relatively large gear ||4 may vmesh Vwith. the relatively small gear ||1. lever |20 is connected to a shaft |2| which car- The 'ries a shifter 'fork |22 which engages an annular groove provided between the gears I4 and `l I5.. This permits a substantial change of speed by Shifting the lever |20 as will be readily apparent.

DependingI fromthe underside ofthe work careived the traverse screw |26 provided as an exteiisi'on of the traverse shaft IIB. The motor HU causes traverse of the carriage through the gearing described above and the traverse nut and screw. The rate of traverse may be varied by the gear shifting mechanism described above. Suitable means (not shown) are provided for reversing the motor Illl to effect return means for effecting traverse on the carriage 20. It will be observed that the traverse of the carriage 20 by the motor H0 is entirely independent of the means for effecting relative timed rotation of the hob and work spindles by the motor 45, but that this traverse introduces a compensating rotation to the Work spindle Il@ by virtue of the helical splined relationship of the members 83 and 81. This permits traverse to be carried out at diierent rates and specifically will permit the hobbing operation to be carried out at a desired slow rate,

after which return traverse to initial position ,A

may be carried out rapidly.

In the specic embodiment of the hobbing machine illustrated relative traverse is in a xed horizontal direction as is determined by the location of the ways I2. However, both the Work spindle and the hob spindle are independently angularly adjustable about a vertical axis so that the direction of relative traverse between the spindles may be at any desired angle with respect thereto. of a method of hobbing which I refer to as "diagonal traverse. In the past the conventional method of hobbing has been to provide relative traverse between the work gear and the hob in a direction parallel to the axis of the Work. By employing a relative traverse which extends at an oblique angle to the axes of both the work spindle and the hob spindle, it is possible to provide a hobbing action which will produce accurately finished gears at a high rate of speed and with increased hob life, since the cutting action is distributed longitudinally over a predetermined portion of the hob during each hobbing stroke. This is to be contrasted with the prior conventional method in which for each setting of the hob the most severe cutting action was concentrated at a specific zone of the hob. In the past efforts have been made to overcome this difficulty which included provision for shifting the hob axially between bobbing operations u.

or for providing an almost imperceptibly slow axial feed of the hob. The present machine obtains improved results over either of these two methods by automatically introducing a distribution of the wear longitudinally7 of the hob during l each cutting cycle. In addition to the foregoing advantage the present hobbing machine permits a very accurate control of lead since with a single splined assembly made up of the parts 83 and 81, it is possible to produce slight variations in lead on the work gear by changing the angle between the direction of relative traverse and the axis of the work spindle. Thus while relatively large changes in relative speed between the hob and work piece will be made by substituting different sets of change gears for the gears III, i12, such gears are not provided to take care of an infinite number of ratios. Thus a particular set of change gears may produce a ratio between the hob spindle and the work spindle which is l not precisely that desired. This ratio may be modified by substituting diierent helically splined members for the members 83 and 81 and ne variations in lead may be accomplished by angular-adjustments of the Work support and This permits the employment d the hob support Ways I2.

Reference is now made to Figure 5 which illustrates a simplification of the hobbing machine which may be made in the event that the feature of angular adjustability of the work support 25 is not required. In this case the shaft instead of carrying the bevel gear illustrated in Figure 2 is provided with a cylindrical gear 130 which meshes with a second cylindrical gear l3l mounted directly on the work spindle m6. In this case the bevel gears 90, 9|, 96, 91 and 98 are not required, since there is no necessity for preserving continuity of a train of gears during angular adjustment of the work table.

The drawings and the foregoing specification constitute a description of the improved hobbing machine in such full, clear, concise and exact terms as to enable any person skilled in the art to practice the invention, the scope of which is indicated by the appended claims.

What I claim as my invention is:

l. A gear bobbing machine comprising a frame, having a bed thereon, a work carriage slidable on said bed, a hob support overlying said carriage and angularly adjustable about a vertical axis, a hob spindle on said hob support, gearing for rotating said hob spindle including a gear whose axis coincides with the axis of adjustment of said hob support to drive said hob spindle in all positions of angular adjustment, a work support angularly adjustable about a vertical axis on said carriage, a work spindle -on said work support, gearing for rotating said work spindle including a gear whose axis coincides with the axis of adjustment of said work support to drive said work spindle in all positions of angular adjustment, said gearing including common drive mea-ns to effect timed rotation ci" .said hob and worin spindles, means independent of said gearing for eecting traverse of said carriage, and helically splined means in said work spindle gearing relatively axially slidable upon traverse ci said carriage to superimpose a compensating rotation on said work spindle in accordance with traverse.

2. A gear hobbing machine comprising a frame, having a bed thereon, fixed ways on said bed, a work carriage slidable on said ways, a hob support overlying said carriage and angularly adjustable about a vertical axis, a hob spindle on said hob support, gearing for rotating said hob spindle including a gear whose axis coincides with the axis of adjustment of said hob support to drive said hob spindle in all positions of angular adjustment, a work support angularly adjustable about a vertical axis on said carriage, a work spindle on said work support, gearing for rotating said worlr spindle including a gear Whose axis coincides with the axis of adjustment oi said work spindle to drive said Work spindle in all positions or" angular adjustment, said gearing including common drive means to elect timed rotation oi' said hob and work spindles, means independent of said gearing' for effecting traverse of said carriage on said ways, and helically splined means in said Work spindle gearing relatively axially slidable upon traverse of said carriage to superimpose a compensating rotation on said work spindle in accordance with traverse.

[3. In a bobbing machine including a hob spindle and a work spindle and connected gear trains for rotating said spindles, a carriage mounting said work spindle for traverse in a direction which occupies a plane parallel to the axes of said spind1essaid carriage carrying a su reIatve te the direction of.

an axis perpedicular to .both of said spindles] 14. A gear hobbing machine for machining the teeth of gears comprising a frame, a carriage slidable on said frame, Work spindle on said carriage, a tool spindle on said frame for a Wormlike tool, means mounting said tool spindle for angular adjustment about an axis perpendicular to the axes of both of said spindles to bring a Worm-like hobbing tool and work piece Vinto a crossed and non-parallel operating relationship equivalent to the meshing relationship of a worm and Worm gear, drive means for said spindles comprising a motor and gearing connecting said motor to both of said spindles, said gearing being eifective to rotate said spindles in the timed relationship proper for meshed rotation of a. Worm and Worm gear having the same number of teeth as the tool and work piece, feeding means for traversing said carriage in a direction to cause the action of the tool to progress from one side to the other of the Work piece, and master lead control compensating means comprising a pair of coaxial helically splined members included in the gearing connecting said motor with said Work spindle, said members being relatively axially slidable upon feeding traverse of said carriage, said work spindle being mounted for angular adiustment in a plane containing its axis and parallel to the direction of traverse of said carriage and parallel to said tool spindle.

[15. A gear hobbing machine as dened in claim 14 in which said work spindle is parallel to the direction of traverse of said carriage] [16. A gear bobbing machine as defined in claim 14 in which. said Work spindle is mounted for angular adjustment in the plane containing its axis and parallel to the direction of traverse of said carriage and parallel to said tool spindle] [17. A gear bobbing machine yas deiined in claim 14 in which said feeding means comprises a feed screw mechanism for traversing said carriage, and a separate motor drive for said mechanism] [18. A gear bobbing machine comprising a frame, a carriage mounted for horizontal sliding movement on said frame, a work spindle on said carriage having its axis parallel to the direction of traverse of said carriage, a tool spindle overhanging said carriage, means mounting said tool spindle for angular adjustment in a horizontal plane, drive means for said spindles comprising a motor and gearing connecting said motor to both of said spindles, feeding means for traversing said carriage, and master lead control compensating means comprising a pair of coaxial helically splined members in the gearing connecting said motor to said work spindle, said members being relatively axially slidable upon traverse of said carriage] [19. A gear hobbing machine as defined in claim 18 in which said splined members are located in said gearing closely adjacent to said Work spindle] [20. A gear ho-bbing machine as dened in claim 18 in which said feeding means comprises a feed screw mechanism, and means for changing the speed of said feeding means independent of the geared rotation of said spindles] [21. A gear hobbing machine as deiined in claim 1S in which said feeding means comprises a separate motor and feed screw mechanism between said frame and carriage] [22. A gear hobbing machine comprising a frame, a Work carriage slidable on said frame, a Work spindle on said carriage, a hob spindle on said frame, a motor, driving gears interconnecting both of said spindles. With said motor including a separate train of gears for driving each .of said spindles in denitely timed geared rotation, feed means for etecting'ftraverse of said carriage, the

train of gears for driving said Work spindle including a .Worm and Worm gear in which the ,sating means responsive to traversev of said carriageto super-impose an additional rotation on said Work spindle upon the geared rotation there- '.ofin` accordance with the lead ofthe Work gear `being hobbedj'ancl the rate of traverse of said carjriage, said compensating means comprising a pair -of coaxial helically splined members in the gear train for driving the Work spindleand located therein intermediate said worm and worm gear and said Work spindle, said splined members being relatively slidable axially upon ytraverse of said oarriagef! [23. A gear hobbing machine as dened in claim 22 in which said work spindle and said helically splined members are parallel to the direction of traverse of said carriage] [24. A gear hobbing machine as defined in claim 23 in which the means for effecting traverse of the carriage comprises a separate motor and feed screw mechanism] 25. A gear hobbing machine comprising a rotary hob spindle, a rotary work spindle, rotary drive means comprising a motor, gear trains connecting said motor to both of said spindles, the gear train driving said work spindle including a worm driving a worm gear, traverse mechanism independent of said rotary drive means for traversing said work spindle in a direction parallel to its axis, and lead compensating mechanism comprising an internal helically splined sleeve secured to said. worm gear, and an externally helically splined member slidably received in said sleeve, said member being included in the gear train driving said work spindle, and being axially movable relative to said sleeve upon traverse of said work spindle.

26'. A gear hobbing machine comprising a trame, a work carriage slidable on said frame, av

wo-rk spindle on said carriage, a hob spindle on said frame, a motor, driving gears interconnecting both of said spindles with said motor including a separate train of gears for driving each of said spindles in definitely timed geared relation, feed means comprising a separate motor and ,feed screw mechanism for egecting traverse of said carriage, the train of gears .for driving said work spindle including a worm and worm gear in which the worm drives the worm gear, said worm and worm gear being located in the gear train relatively close to the work spindle, master lead compensating means responsive to traverse of said carriage to saperimpose an additional rotation on said work spindle upon the geared rotation thereof in accordance with the lead of the work gear being hobbed and the rate of traverse of said carriage, said compensating means comprising a vpair of coaxial helically splined members in the gear train for driving the work spindle and located therein intermediate said worm and worm gear and said work spindle and parallel to the direction of traverse of said carriage, said splined members being relatively slidable 'axially upon traverse of said carriage.

27. A. hobbing machine comprising a rotary hob J1 piudle. wete@ mage, .wenns sleppontiny 0f Saidpildes :im indpgns'flLf-mauar adjustment,ebmtmesimmdiuer @both Qfsaid .seimila www drive ,taf 119th Qf vwid @miles a :zeer freins 9on- ,ilectina mamma? toxseiclindles, a Aim: Le 'worm maar in the' `,sneer .tryin ,driving `sata work Spindle cemnwating mechenism dfivl by Said in said :lest 'menaned gear train, useid mechansmmnpnkng a mir of 'filelial'ly sfnliued membewtmzzersemeans indezzendm of Lsais! romy drive for effeny traverse pf ma .spindle in ,a .diresmtagllel t9 pf seidinmbem me @I Said 4s'izl1`11eff-1 members-being menate!! .for mtatim Ain fixed Pqsion :re @tipe i9 .said geen, said ether spliuemmbef b 'ymemtively ometed t9 .said ma e mancmmt Meer Altravefse of ,sa and heie slidablg/ @walled wim' 'md bile .mim

,Number `12 n28. A machine as .deflnedin claim 271'1L which qqz'd vnmlzafzjs includes a -slow feed for `cut- -tipvgmgears 'and a ,rapid return traverse, and means lf or selectively rendering said slow feed and Trapid 

